Inflammation is the body's attempt at self-protection; the aim being
to remove harmful stimuli, including damaged cells, irritants, or
pathogens - and begin the healing process.
When something harmful or irritating affects a part of our body, there
is a biological response to try to remove it, the signs and symptoms of
inflammation, specifically acute inflammation, show that the body is
trying to heal itself.
Inflammation does not mean infection, even when an infection causes
inflammation. Infection is caused by a bacterium, virus or fungus, while
inflammation is the body's response to it.
The word
inflammation comes from the Latin
"inflammo", meaning
"I set alight, I ignite".
Inflammation is part of the body's immune response. Initially, it is
beneficial when, for example, your knee sustains a blow and tissues need
care and protection. However, sometimes inflammation can cause further
inflammation; it can become self-perpetuating. More inflammation is
created in response to the existing inflammation.
According to Medilexicon's medical dictionary,
Inflammation is:
"A fundamental pathologic process consisting of a dynamic complex of
histologically apparent cytologic changes, cellular infiltration, and
mediator release that occurs in the affected blood vessels and adjacent
tissues in response to an injury or abnormal stimulation caused by a
physical, chemical, or biologic agent, including the local reactions and
resulting morphologic changes; the destruction or removal of the
injurious material; and the responses that lead to repair and healing.
The so-called cardinal signs of inflammation are rubor, redness; calor, heat (or warmth); tumor,
swelling; and dolor, pain; a fifth sign, functio laesa, inhibited or
lost function, is sometimes added. All these signs may be observed in
certain instances, but none is necessarily always present."
Plaque in coronary artery disease linked to inflammation - scientists from Stanford University, California, linked 25 new genetic regions to coronary artery disease.
They found that people with coronary artery disease, the leading cause
of death globally, are most likely predisposed to the disease because
they have gene variants linked to inflammation.
Inflammation helps wounds heal
Our immediate reaction to a swelling is to try to bring it down. Bearing
in mind that inflammation is an essential part of the body's attempt to
heal itself, patients and doctors need to be sure that the treatments
to reduce swelling are absolutely necessary and to not undermine or slow
down the healing process.
The first stage of inflammation is often called irritation, which then
becomes inflammation - the immediate healing process. Inflammation is
followed by suppuration (discharging of pus).
Then there is the granulation stage, the formation in wounds of tiny,
rounded masses of tissue during healing. Inflammation is part of a
complex biological response to harmful stimuli. Without inflammation,
infections and wounds would never heal.
Neuroscientists at the Lerner Research Institute at the Cleveland Clinic in Ohio found that inflammation actually helps to heal
damaged muscle tissue. Their findings clash with how sportspeople with
inflammation are treated - health professionals always try to control
the inflammation to encourage healing. The researchers say their
findings may lead to new therapies for acute muscle injuries caused by
freeze damage, medications, chemicals and trauma.
Lan Zhou, M.D., Ph.D., said that patients should be very closely
monitored when therapies to combat inflammation are used to make sure
that the benefits of inflammation are not completely eliminated.
Inflammation is part of our innate immunity
Our
innate immunity is what is naturally present in our bodies when we are born, and not the
adaptive immunity
we get after an infection or vaccination. Innate immunity is generally
non-specific, while adaptive immunity is specific to one pathogen:
Whooping cough vaccine - example of immunity being specific to one pathogen
After being vaccinated for whooping cough (pertussis), we develop immunity to Bordetella pertussis or Bordetella parapertussis,
types of bacteria that cause pertussis. This is an example of adaptive
immunity - the immunity was not there before receiving the vaccine.
Inflammation is seen as a mechanism of innate immunity.
What is the difference between chronic inflammation and acute inflammation?
Acute inflammation - starts rapidly (rapid onset) and quickly
becomes severe. Signs and symptoms are only present for a few days, but
in some cases may persist for a few weeks.
Examples of diseases, conditions, and situations which can result in acute inflammation include: acute bronchitis, infected ingrown toenail, sore throat from a cold or flu, a scratch/cut on the skin, exercise (especially intense training), acute appendicitis, acute dermatitis, acute tonsillitis, acute infective meningitis, acute sinusitis, or a blow.
Chronic inflammation - this means long-term inflammation, which can last for several months and even years. It can result from:
- Failure to eliminate whatever was causing an acute inflammation
- An autoimmune response to a self antigen - the immune system attacks healthy tissue, mistaking it (them) for harmful pathogens.
- A chronic irritant of low intensity that persists
Examples of diseases and conditions with chronic inflammation include: asthma, chronic peptic ulcer, tuberculosis, rheumatoid arthritis, chronic periodontitis, ulcerative colitis and Crohn's disease, chronic sinusitis, and chronic active hepatitis (there are many more).
Our infections, wounds and any damage to tissue would never health
without inflammation - tissue would become more and more damaged and the
body, or any organism, would eventually perish.
However, chronic inflammation can eventually cause several diseases and conditions, including some cancers, rheumatoid arthritis, atherosclerosis, periodontitis, and hay fever. Inflammation needs to be well regulated.
What happens during acute inflammation?
Within a few seconds or minutes after tissue is injured, acute
inflammation starts to occur. The damage may be a physical one, or might
be caused by an immune response.
Three main processes occur before and during acute inflammation:
- Arterioles, small branches of arteries that lead to capillaries that
supply blood to the damaged region dilate, resulting in increased blood
flow
- The capillaries become more permeable, so fluid and blood proteins can move into interstitial spaces (spaces between tissues).
- Neutrophils, and possibly some macrophages migrate out of the
capillaries and venules (small veins that go from a capillary to a vein)
and move into interstitial spaces. A neutrophil is a type of
granulocyte (white blood cell), it is filled with tiny sacs which
contain enzymes that digest microorganisms. Macrophages are also a type
of white blood cells that ingests foreign material.
Klaus Ley, M.D., a scientist at the La Jolla Institute for Allergy & Immunology, reported in a study published in Nature
that neutrophils are the human body's first line of defense; they are
the main cells that protect us from bacterial infections. Their
protective function is a positive one, however, they also have
inflammatory properties that may eventually lead to heart disease and several autoimmune diseases, such as lupus. Effectively manipulating neutrophils is vital in disrupting inflammatory diseases.
When our skin is scratched (and the skin is not broken), one may see a
pale red line. Soon the area around that scratch goes red, this is
because the arterioles have dilated and the capillaries have filled up
with blood and become more permeable, allowing fluid and blood proteins
to move into the space between tissues.
Edema - the area then swells as further fluid builds up in the interstitial spaces.
The five cardinal signs of acute inflammation - "PRISH"
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An ingrown toenail with the five PRISH signs; pain, redness, immobility, swelling and heat
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- Pain - the inflamed area is likely to be painful, especially
when touched. Chemicals that stimulate nerve endings are released,
making the area much more sensitive.
- Redness - this is because the capillaries are filled up with more blood than usual
- Immobility - there may be some loss of function
- Swelling - caused by an accumulation of fluid
- Heat - as with the reason for the redness, more blood in the affected area makes it feel hot to the touch
The five classical signs of inflammation
Although Latin terms are still used widely in Western medicine, local
language terms, such as English, are taking over. PRISH is a more modern
acronym which refers to the signs of inflammation. The traditional
Latin based terms have been around for two thousand years:
- Dolor - Latin term for "pain"
- Calor - Latin term for "heat"
- Rubor - which in Latin means "redness"
- Tumor - a Latin term for "swelling"
- Functio laesa - which in Latin means "injured function", which can also mean loss of function
Dolor, Calor, Rubor, and
Tumor were first described and
documented by Aulus Cornelius Celsus (ca 25 BC-ca 50), a Roman
encyclopaedist. Celcius is famous for creating
De Medicina, which is thought to be the only surviving section of a vast encyclopedia.
De Medicina was the main source of medical reference in the Roman world for pharmacy, surgery, diet and some other medical fields.
Functio laesa - it is not clear who first described and
documented the fifth sign. The majority of attributions have gone to
Thomas Sydenham (1624-1689) an English physician and Rudolph Carl
Virchow (1821-1902), a German doctor, biologist, politician and
pathologist. Virchow is seen as one of the founders of social medicine.
These five acute inflammation signs are only relevant when the affected
area is on or very close to the skin. When inflammation occurs deep
inside the body, such as an internal organ, only some of the signs may
be detectable. Some internal organs may not have sensory nerve endings
nearby, so there is be no pain, as is the case with some types of pneumonia
(acute inflammation of the lung). If the inflammation from pneumonia
pushes against the parietal pleura (inner lining of the surface of the
chest wall), then there is pain.
Acute and chronic inflammation compared
The lists below show the difference between chronic and acute
inflammation regarding the causative agents, which major cells are
involved, features regarding onset, duration, and outcomes:
Acute Inflammation
- Causative agents - harmful bacteria or injury to tissue
- Major cells involved - mainly neutrophils, basophils (in the
inflammatory response), and eosinophils (response to parasites and
worms), and mononuclear cells (macrophages, monocytes)
- Primary mediators - eicosanoids, vasoactive amines
- Onset (when does the inflammation start) - straight away
- Duration - short-lived, only a few days
- Outcomes - the inflammation either gets better (resolution), develops into an abscess, or becomes a chronic inflammation
Chronic inflammation
- Causative agent - non-degradable pathogens that cause
persistent inflammation, infection with some types of viruses,
persistent foreign bodies, overactive immune system reactions
- Major cells involved - Macrophages, lymphocytes, plasma cells (these three are mononuclear cells), and fibroblasts
- Primary mediators - reactive oxygen species, hydrolytic enzymes, IFN-Îł and other cytokines, growth factors
- Duration - from several months to years
- Outcomes - the destruction of tissue, thickening and scarring of connective tissue (fibrosis), death of cells or tissues (necrosis)
Sleep quality and duration impacts on inflammation risk
Scientists at Emory University School of Medicine in Atlanta, Georgia, found in a study that sleep deprivation or poor sleep quality raise inflammation, which in turn increase the risk of developing heart disease and stroke.
The team gathered data on 525 middle-aged volunteers who had completed
the Pittsburgh Sleep Quality Index (PSQI) questionnaire, which asked
detailed questions about sleep quality and duration.
They tested the participants' levels of various inflammatory markers,
and then tried to see whether they could link them to quality and
duration of sleep.
The authors concluded:
"The researchers concluded that:
"Poor sleep quality, and short sleep durations are associated with higher levels of inflammation."